Remi's Linux IDE
This is an emulator that runs Linux in a x86-64 virtual machine.
Not many people have heard about this, but it does exist, and it allows you to code more easily for linux when you are in school.
Note: This is for advanced linux users looking to code programs, not only as a novelty. For a less practical use, check out the Online RISC Linux.
The project was made by Remi Sharrock.